/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.test.util;

import org.springframework.aop.framework.Advised;
import org.springframework.aop.support.AopUtils;
import org.springframework.util.Assert;

/**
 * {@code AopTestUtils} is a collection of AOP-related utility methods for
 * use in unit and integration testing scenarios.
 *
 * <p>For Spring's core AOP utilities, see
 * {@link org.springframework.aop.support.AopUtils AopUtils} and
 * {@link org.springframework.aop.framework.AopProxyUtils AopProxyUtils}.
 *
 * @author Sam Brannen
 * @author Juergen Hoeller
 * @see org.springframework.aop.support.AopUtils
 * @see org.springframework.aop.framework.AopProxyUtils
 * @see ReflectionTestUtils
 * @since 4.2
 */
public abstract class AopTestUtils {

    /**
     * Get the <em>target</em> object of the supplied {@code candidate} object.
     * <p>If the supplied {@code candidate} is a Spring
     * {@linkplain AopUtils#isAopProxy proxy}, the target of the proxy will
     * be returned; otherwise, the {@code candidate} will be returned
     * <em>as is</em>.
     *
     * @param candidate the instance to check (potentially a Spring AOP proxy;
     *                  never {@code null})
     * @return the target object or the {@code candidate} (never {@code null})
     * @throws IllegalStateException if an error occurs while unwrapping a proxy
     * @see Advised#getTargetSource()
     * @see #getUltimateTargetObject
     */
    @SuppressWarnings("unchecked")
    public static <T> T getTargetObject(Object candidate) {
        Assert.notNull(candidate, "Candidate must not be null");
        try {
            if (AopUtils.isAopProxy(candidate) && candidate instanceof Advised) {
                Object target = ((Advised) candidate).getTargetSource().getTarget();
                if (target != null) {
                    return (T) target;
                }
            }
        } catch (Throwable ex) {
            throw new IllegalStateException("Failed to unwrap proxied object", ex);
        }
        return (T) candidate;
    }

    /**
     * Get the ultimate <em>target</em> object of the supplied {@code candidate}
     * object, unwrapping not only a top-level proxy but also any number of
     * nested proxies.
     * <p>If the supplied {@code candidate} is a Spring
     * {@linkplain AopUtils#isAopProxy proxy}, the ultimate target of all
     * nested proxies will be returned; otherwise, the {@code candidate}
     * will be returned <em>as is</em>.
     *
     * @param candidate the instance to check (potentially a Spring AOP proxy;
     *                  never {@code null})
     * @return the target object or the {@code candidate} (never {@code null})
     * @throws IllegalStateException if an error occurs while unwrapping a proxy
     * @see Advised#getTargetSource()
     * @see org.springframework.aop.framework.AopProxyUtils#ultimateTargetClass
     */
    @SuppressWarnings("unchecked")
    public static <T> T getUltimateTargetObject(Object candidate) {
        Assert.notNull(candidate, "Candidate must not be null");
        try {
            if (AopUtils.isAopProxy(candidate) && candidate instanceof Advised) {
                Object target = ((Advised) candidate).getTargetSource().getTarget();
                if (target != null) {
                    return (T) getUltimateTargetObject(target);
                }
            }
        } catch (Throwable ex) {
            throw new IllegalStateException("Failed to unwrap proxied object", ex);
        }
        return (T) candidate;
    }

}
